Spring-stretch-reducing window sash balance

Abstract

A sash coupling is adapted to be connected to one side of a sash which slides vertically in parallel channel sash guides mounted within a sliding sash window frame. Secured to the top of the sash coupling is the lower end of a flexible sash cable, the outer end of which extends upward to and around a stationary outer pulley pivotally mounted on a transverse pulley support at the top of the sash guide, whence an intermediate section of the cable extends downward to and around a vertically-movable traveling pulley mounted on a balancing-spring coupling to which the upper end of the elongated sash-balancing tension spring is hooked, whence an inner section of the cable extends upward to an anchorage on the upper end of the sash guide. The lower end of the elongated sash-balancing spring is hooked over the lower end of the sash guide. For a double-hung sliding sash installation, the upper sash is balanced in a similar manner. For By arranging in this manner the sash cable in three sections around two pulleys, the stretch of the sash balancing spring is reduced to but a fraction of the distance through which the sash is moved during the opening operation thereof. This is in contrast to the much greater stretch with a consequently greater varation in the balancing force applied to the sash by a single elongated sash balancing spring stretched directly between the sash and the top of the channel sash guide.

I claim: 
     
       1. A self-contained spring-stretch-reducing sash balance construction for double-hung, sliding sash windows to be mounted in and between laterally spaced opposite vertical sides of a sliding sash window frame, that improvement which comprises: (a) a separately mountable, elongate slide housing for at least one side of the window having a back face portion to lie along the side of a window frame. said slide housing having a closed front center panel to be spaced outwardly from the back face to form a first, central, elongate, vertical chamber open at the back, and spaced, parallel, elongate sash guides spaced laterally to each side of said center panel, each sash guide being slotted lengthwise and spaced outwardly from the back face of the housing to provide a vertical reentrant retaining guide track chamber for a sash coupling element with common vertical walls between said central chamber and said guide track chambers,   (b) a sash balance header element supported horizontally at the top and within the confines of said slide housing having spaced pulley chambers formed therein at the top of and open to said vertical chamber and said guide track chambers,   (c) a stationary pulley rotatably supported in each said pulley chamber above said respective guide tracks in said slide housing,   (d) elongate balancing springs disposed in parallel spaced relation in said central vertical chamber anchored at one end adjacent the bottom of said slide housing with movable ends extending up into said central vertical chamber,   (e) a traveling pulley element affixed to the upper ends of each of said springs, and   (f) a flexible cable on each side of said slide housing having a fixed end anchored centrally of said header above said central vertical chamber and a movable end connected to sash coupling elements in the respective vertical guide track chambers, each said cable having a first section in said central vertical chamber extending from said header to and around said traveling pulley and a second section in said vertical chamber extending from said first section beyond said traveling pulley into one of the spaced header vertical guide track chambers around a stationary pulley above said chambers, and a third section in a guide track chamber extending from said second section beyond said stationary pulley to a sash coupling in said respective guide track chambers.     
     
     
       2. A device as defined in claim 1 in which said header element comprises an integral molded element in the form of a rectangular box having side walls, end walls, and transverse intermediate walls parallel to said end walls, said side walls and said intermediate walls forming a central well, and a perforate bottom in said well to serve as an anchor point for each said cable, said side walls beyond said intermediate walls being notched from the top to provide spaced bearing journals, and pulleys in said header having integral axles journaled in said notches and pulley sheaves between said side walls. 
     
     
       3. A device as defined in claim 2 in which the top of the said common walls between said chambers are notched downwardly and the bottom of said side walls of said header element are notched upwardly so said walls can interengage to stabilize said header element in said slide housing. 
     
     
       4. A device as defined in claim 1 in which said traveling pulley element comprises an integral U-shaped plastic element having a bight portion to engage a balancing spring and spaced legs with opposed axle journal openings and resiliently spreadable to allow insertion of a pulley having integral axles at each side to seat and run in said journal openings.